Semiconductor Device and Method

ABSTRACT

An embodiment method includes: forming fins extending from a semiconductor substrate; depositing an inter-layer dielectric (ILD) layer on the fins; forming masking layers on the ILD layer; forming a cut mask on the masking layers, the cut mask including a first dielectric material, the cut mask having first openings exposing the masking layers, each of the first openings surrounded on all sides by the first dielectric material; forming a line mask on the cut mask and in the first openings, the line mask having slot openings, the slot openings exposing portions of the cut mask and portions of the masking layers, the slot openings being strips extending perpendicular to the fins; patterning the masking layers by etching the portions of the masking layers exposed by the first openings and the slot openings; and etching contact openings in the ILD layer using the patterned masking layers as an etching mask.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as, for example, personal computers, cell phones, digital cameras,and other electronic equipment. Semiconductor devices are typicallyfabricated by sequentially depositing insulating or dielectric layers,conductive layers, and semiconductor layers of material over asemiconductor substrate, and patterning the various material layersusing lithography to form circuit components and elements thereon.

The semiconductor industry continues to improve the integration densityof various electronic components (e.g., transistors, diodes, resistors,capacitors, etc.) by continual reductions in minimum feature size, whichallow more components to be integrated into a given area. However, asthe minimum features sizes are reduced, additional problems arise thatshould be addressed.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates an example of a FinFET in a three-dimensional view,in accordance with some embodiments.

FIGS. 2A through 5B are various views of intermediate stages in themanufacturing of FinFETs, in accordance with some embodiments.

FIGS. 6A through 10B are various views of further intermediate stages inthe manufacturing of FinFETs, in accordance with some embodiments.

FIGS. 11A through 12B are various views of further intermediate stagesin the manufacturing of FinFETs, in accordance with some otherembodiments.

FIGS. 13A through 15B are various views of further intermediate stagesin the manufacturing of FinFETs, in accordance with some otherembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In accordance with some embodiments a cut mask and a line mask are usedin combination to define regions in which contacts will be formed in adielectric layer, such as an inter-layer dielectric (ILD) layer. Theline mask has slotted openings that extend a first direction, and thecut mask has dielectric lines that extend in a perpendicular seconddirection, intersecting the slotted openings. The slotted openingsdefine regions in which contacts will be formed, and the dielectriclines define regions in which contacts will not be formed. The line maskfurther includes trim portions that extend in the first direction, anddefine additional areas in which contacts will not be formed.Specifically, unused areas that would otherwise contain dummy contactsare excluded from contact formation with the trim portions of the linemask. By reducing the amount of dummy contacts, a parasitic capacitanceon other conductive features may be avoided. Reducing the parasiticcapacitance of the FinFETs can be particularly advantageous for someapplications, such as ring oscillators, where performance can beimproved by up to 1%.

FIG. 1 illustrates an example of simplified Fin Field-Effect Transistors(FinFETs) in a three-dimensional view, in accordance with someembodiments. Some other features of the FinFETs (discussed below) areomitted for illustration clarity. The illustrated FinFETs may beelectrically connected or coupled in a manner to operate as, forexample, one transistor or multiple transistors, such as twotransistors.

The FinFETs comprise fins 52 extending from a substrate 50. Shallowtrench isolation (STI) regions 56 are disposed over the substrate 50,and the fins 52 protrude above and from between neighboring STI regions56. Although the STI regions 56 are described/illustrated as beingseparate from the substrate 50, as used herein the term “substrate” maybe used to refer to just the semiconductor substrate or a semiconductorsubstrate inclusive of isolation regions. Additionally, although thefins 52 are illustrated as being a single, continuous material of thesubstrate 50, the fins 52 and/or the substrate 50 may comprise a singlematerial or a plurality of materials. In this context, the fins 52refers to the portions extending between the neighboring STI regions 56.

Gate dielectrics 82 are along sidewalls and over top surfaces of thefins 52, and gate electrodes 84 are over the gate dielectrics 82.Source/drain regions 70 are disposed in opposite sides of the fin 52with respect to the gate dielectrics 82 and gate electrodes 84. Gatespacers 66 separate the source/drain regions 70 from the gatedielectrics 82 and gate electrodes 84. In embodiments where multipletransistors are formed, the source/drain regions 70 may be sharedbetween various transistors. In embodiments where one transistor isformed from multiple fins 52, neighboring source/drain regions 70 may beelectrically connected, such as through coalescing the source/drainregions 70 by epitaxial growth, or through coupling the source/drainregions 70 with a same source/drain contact.

FIG. 1 further illustrates several reference cross-sections.Cross-section A-A is along a longitudinal axis of the fin 52 and in adirection of, for example, a current flow between the source/drainregions 70 of a FinFET. Cross-section B-B is perpendicular tocross-section A-A and is along a longitudinal axis of the gateelectrodes 84. Cross-section C-C is perpendicular to cross-section A-Aand extends through source/drain regions 70 of the FinFET. Subsequentfigures refer to these reference cross-sections for clarity.

Some embodiments discussed herein are discussed in the context ofFinFETs formed using a gate-last process. In other embodiments, agate-first process may be used. Also, some embodiments contemplateaspects used in planar devices, such as planar FETs.

FIGS. 2A through 5B are cross-sectional views of intermediate stages inthe manufacturing of FinFETs, in accordance with some embodiments. FIGS.2A, 3A, 4A, and 5A are cross-sectional views illustrated along referencecross-section A-A in FIG. 1, except for multiple fins/FinFETs. FIGS. 2B,3B, 4B, and 5B are cross-sectional views illustrated along referencecross-section B-B in FIG. 1, except for multiple fins/FinFETs. FIGS. 2Cand 2D are cross-sectional views illustrated along referencecross-section C-C in FIG. 1, except for multiple fins/FinFETs.

In FIGS. 2A and 2B, a substrate 50 is provided. The substrate 50 may bea semiconductor substrate, such as a bulk semiconductor, asemiconductor-on-insulator (SOI) substrate, or the like, which may bedoped (e.g., with a p-type or an n-type dopant) or undoped. Thesubstrate 50 may be a wafer, such as a silicon wafer. Generally, an SOIsubstrate is a layer of a semiconductor material formed on an insulatorlayer. The insulator layer may be, for example, a buried oxide (BOX)layer, a silicon oxide layer, or the like. The insulator layer isprovided on a substrate, typically a silicon or glass substrate. Othersubstrates, such as a multi-layered or gradient substrate may also beused. In some embodiments, the semiconductor material of the substrate50 may include silicon; germanium; a compound semiconductor includingsilicon carbide, gallium arsenic, gallium phosphide, indium phosphide,indium arsenide, and/or indium antimonide; an alloy semiconductorincluding SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; orcombinations thereof. For example, when p-type devices are formed, thesubstrate 50 may be a strained material such as silicon germanium(Si_(x)Ge_(1−x), where x can be in the range of 0 to 1) having agermanium concentration in the range of about 0% to about 40%, such thatFinFETs with p-type fully strained channel (PFSC) regions are formed.

The substrate 50 has a region 50N and a region 50P. The region 50N canbe for forming n-type devices, such as NMOS transistors, e.g., n-typeFinFETs. The region 50P can be for forming p-type devices, such as PMOStransistors, e.g., p-type FinFETs. The region 50N may be physicallyseparated from the region 50P, and any number of device features (e.g.,other active devices, doped regions, isolation structures, etc.) may bedisposed between the region 50N and the region 50P.

Fins 52 are formed extending from the substrate 50. The fins 52 aresemiconductor strips. In some embodiments, the fins 52 may be formed inthe substrate 50 by etching trenches in the substrate 50. The etchingmay be any acceptable etch process, such as a reactive ion etch (RIE),neutral beam etch (NBE), the like, or a combination thereof. The etchmay be anisotropic. After formations, the fins 52 have a width W₁, andfins 52 in a same region 50N/50P are spaced apart by a pitch P₁. Thewidth W₁ can be in the range of about 11 nm to about 14 nm, and thepitch P₁ can be in the range of about 55 nm to about 60 nm.

The fins may be patterned by any suitable method. For example, the finsmay be patterned using one or more photolithography processes, includingdouble-patterning or multi-patterning processes. Generally,double-patterning or multi-patterning processes combine photolithographyand self-aligned processes, allowing patterns to be created that have,for example, pitches smaller than what is otherwise obtainable using asingle, direct photolithography process. For example, in one embodiment,a sacrificial layer is formed over a substrate and patterned using aphotolithography process. Spacers are formed alongside the patternedsacrificial layer using a self-aligned process. The sacrificial layer isthen removed, and the remaining spacers may then be used to pattern thefins.

STI regions 56 are formed over the substrate 50 and between neighboringfins 52. As an example to form the STI regions 56, an insulationmaterial is formed over the intermediate structure. The insulationmaterial may be an oxide, such as silicon oxide, a nitride, the like, ora combination thereof, and may be formed by a high density plasmachemical vapor deposition (HDP-CVD), a flowable chemical vapordeposition (FCVD) (e.g., a chemical vapor deposition (CVD) basedmaterial deposition in a remote plasma system and post curing to make itconvert to another material, such as an oxide), the like, or acombination thereof. Other insulation materials formed by any acceptableprocess may be used. In the illustrated embodiment, the insulationmaterial is silicon oxide formed by a FCVD process. An anneal processmay be performed once the insulation material is formed. In anembodiment, the insulation material is formed such that excessinsulation material covers the fins 52. Some embodiments may utilizemultiple layers. For example, in some embodiments a liner (not shown)may first be formed along a surface of the substrate 50 and the fins 52.Thereafter, a fill material, such as those discussed above may be formedover the liner. A removal process is applied to the insulation materialto remove excess insulation material over the fins 52. In someembodiments, a planarization process such as a chemical mechanicalpolish (CMP), an etch back process, combinations thereof, or the likemay be utilized. The planarization process exposes the fins 52 such thattop surfaces of the fins 52 and the insulation material are level afterthe planarization process is complete. The insulation material is thenrecessed, with remaining portions of the insulation material forming theSTI regions 56. The insulation material is recessed such that upperportions of fins 52 in the region 50N and in the region 50P protrudefrom between neighboring STI regions 56. After the recessing, exposedportions of the fins 52 extend a height H₁ above top surfaces of the STIregions 56. The height H₁ can be greater than about 40 nm, such as inthe range of about 50 nm to about 80 nm. The exposed portions of thefins 52 include what will be channel regions of the resulting FinFETs.

Further, the top surfaces of the STI regions 56 may have a flat surfaceas illustrated, a convex surface, a concave surface (such as dishing),or a combination thereof. The top surfaces of the STI regions 56 may beformed flat, convex, and/or concave by an appropriate etch. The STIregions 56 may be recessed using an acceptable etching process, such asone that is selective to the material of the insulation material (e.g.,etches the material of the insulation material at a faster rate than thematerial of the fins 52). For example, a chemical oxide removal with asuitable etch process using, for example, dilute hydrofluoric (dHF) acidmay be used.

The process described above is just one example of how the fins 52 maybe formed. In some embodiments, the fins may be formed by an epitaxialgrowth process. For example, a dielectric layer can be formed over a topsurface of the substrate 50, and trenches can be etched through thedielectric layer to expose the underlying substrate 50. Homoepitaxialstructures can be epitaxially grown in the trenches, and the dielectriclayer can be recessed such that the homoepitaxial structures protrudefrom the dielectric layer to form fins. Additionally, in someembodiments, heteroepitaxial structures can be used for the fins 52. Forexample, after the insulation material of the STI regions 56 isplanarized with the fins 52, the fins 52 can be recessed, and a materialdifferent from the fins 52 may be epitaxially grown over the recessedfins 52. In such embodiments, the fins 52 comprise the recessed materialas well as the epitaxially grown material disposed over the recessedmaterial. In an even further embodiment, a dielectric layer can beformed over a top surface of the substrate 50, and trenches can beetched through the dielectric layer. Heteroepitaxial structures can thenbe epitaxially grown in the trenches using a material different from thesubstrate 50, and the dielectric layer can be recessed such that theheteroepitaxial structures protrude from the dielectric layer to formthe fins 52. In some embodiments where homoepitaxial or heteroepitaxialstructures are epitaxially grown, the epitaxially grown materials may bein situ doped during growth, which may obviate prior and subsequentimplantations although in situ and implantation doping may be usedtogether.

Still further, it may be advantageous to epitaxially grow a material inregion 50N (e.g., an NMOS region) different from the material in region50P (e.g., a PMOS region). In various embodiments, upper portions of thefins 52 may be formed from silicon germanium (Si_(x)Ge_(1−x), where xcan be in the range of 0 to 1), silicon carbide, pure or substantiallypure germanium, a III-V compound semiconductor, a II-VI compoundsemiconductor, or the like. For example, the available materials forforming III-V compound semiconductor include, but are not limited to,InAs, AlAs, GaAs, InP, GaN, InGaAs, InAlAs, GaSb, AlSb, AlP, GaP, andthe like.

Further, appropriate wells (not shown) may be formed in the fins 52and/or the substrate 50. In some embodiments, a P well may be formed inthe region 50N, and an N well may be formed in the region 50P. In someembodiments, a P well or an N well are formed in both the region 50N andthe region 50P.

In the embodiments with different well types, the different implantsteps for the region 50N and the region 50P may be achieved using aphotoresist or other masks (not shown). For example, a photoresist maybe formed over the fins 52 and the STI regions 56 in the region 50N. Thephotoresist is patterned to expose the region 50P of the substrate 50,such as a PMOS region. The photoresist can be formed by using a spin-ontechnique and can be patterned using acceptable photolithographytechniques. Once the photoresist is patterned, an n-type impurityimplant is performed in the region 50P, and the photoresist may act as amask to substantially prevent n-type impurities from being implantedinto the region 50N, such as an NMOS region. The n-type impurities maybe phosphorus, arsenic, antimony, or the like implanted in the region toa concentration of equal to or less than 10¹⁸ cm⁻³, such as betweenabout 10¹⁷ cm⁻³ and about 10¹⁸ cm⁻³. After the implant, the photoresistis removed, such as by an acceptable ashing process.

Following the implanting of the region 50P, a photoresist is formed overthe fins 52 and the STI regions 56 in the region 50P. The photoresist ispatterned to expose the region 50N of the substrate 50, such as the NMOSregion. The photoresist can be formed by using a spin-on technique andcan be patterned using acceptable photolithography techniques. Once thephotoresist is patterned, a p-type impurity implant may be performed inthe region 50N, and the photoresist may act as a mask to substantiallyprevent p-type impurities from being implanted into the region 50P, suchas the PMOS region. The p-type impurities may be boron, BF₂, indium, orthe like implanted in the region to a concentration of equal to or lessthan 10¹⁸ cm⁻³, such as between about 10¹⁷ cm⁻³ and about 10¹⁸ cm⁻³.After the implant, the photoresist may be removed, such as by anacceptable ashing process.

After the implants of the region 50N and the region 50P, an anneal maybe performed to activate the p-type and/or n-type impurities that wereimplanted. In some embodiments, the grown materials of epitaxial finsmay be in situ doped during growth, which may obviate the implantations,although in situ and implantation doping may be used together.

Dummy gate dielectrics 60 are formed over the fins 52 and dummy gates 62are formed over the dummy gate dielectrics 60. The dummy gatedielectrics 60 and dummy gates 62 may be collectively referred to as“dummy gate stacks,” with each dummy gate stack including a dummy gatedielectric 60 and a dummy gate 62. The dummy gate stacks extend alongsidewalls of the fins 52. Although only one dummy gate stack isillustrated, it should be appreciated that multiple dummy gate stack aresimultaneously formed, and each fin 52 may have multiple dummy gatestacks formed thereon.

As an example of forming the dummy gate dielectrics 60 and dummy gates62, a dummy dielectric layer is formed on the fins 52. The dummydielectric layer may be, for example, silicon oxide, silicon nitride, acombination thereof, or the like, and may be deposited or thermallygrown according to acceptable techniques. A dummy gate layer is formedover the dummy dielectric layer, and a mask layer is formed over thedummy gate layer. The dummy gate layer may be deposited over the dummydielectric layer and then planarized, such as by a CMP. The mask layermay be deposited over the dummy gate layer. The dummy gate layer may bea conductive or non-conductive material and may be selected from a groupincluding amorphous silicon, polycrystalline-silicon (polysilicon),poly-crystalline silicon-germanium (poly-SiGe), metallic nitrides,metallic silicides, metallic oxides, and metals. The dummy gate layermay be deposited by physical vapor deposition (PVD), CVD, sputterdeposition, or other techniques known and used in the art for depositingconductive materials. The dummy gate layer may be made of othermaterials that have a high etching selectivity from the etching ofisolation regions. The mask layer may include, for example, siliconnitride, silicon oxynitride, or the like. In this example, a singledummy gate layer and a single mask layer are formed across the region50N and the region 50P. It is noted that the dummy dielectric layer isshown covering only the fins 52 for illustrative purposes only. In someembodiments, the dummy dielectric layer may be deposited such that thedummy dielectric layer covers the STI regions 56, extending between thedummy gate layer and the STI regions 56. The mask layer is thenpatterned using acceptable photolithography and etching techniques toform masks 64. The pattern of the masks 64 is then transferred to thedummy gate layer by an acceptable etching technique to form dummy gates62. The pattern of the masks 64 is further transferred to the dummydielectric layer to form dummy gate dielectrics 60. The dummy gates 62cover respective channel regions of the fins 52. The pattern of themasks 64 may be used to physically separate each of the dummy gates 62from adjacent dummy gates. The dummy gates 62 may also have a lengthwisedirection substantially perpendicular to the lengthwise direction ofrespective fins 52.

Gate spacers 66 are formed on exposed surfaces of the dummy gates 62,the masks 64, and/or the fins 52. The gate spacers 66 may be formed byconformally depositing an insulating material and subsequently etchingthe insulating material. The insulating material of the gate spacers 66may be silicon nitride, silicon carbon nitride, a combination thereof,or the like. In some embodiments (not shown), the gate spacers 66 areformed from a multi-layered insulating material, and include multiplelayers. For example, the gate spacers 66 may include multiple layers ofsilicon nitride, or may include a layer of silicon oxide disposedbetween two layers of silicon nitride. The etching of the gate spacers66 can be anisotropic. After etching, the gate spacers 66 can havestraight sidewalls or curved sidewalls.

Before or during the formation of the gate spacers 66, implants forlightly doped source/drain (LDD) regions (not explicitly illustrated)may be performed. In the embodiments with different device types,similar to the implants discussed, a mask, such as a photoresist, may beformed over the region 50N, while exposing the region 50P, andappropriate type (e.g., p-type) impurities may be implanted into theexposed fins 52 in the region 50P. The mask may then be removed.Subsequently, a mask, such as a photoresist, may be formed over theregion 50P while exposing the region 50N, and appropriate typeimpurities (e.g., n-type) may be implanted into the exposed fins 52 inthe region 50N. The mask may then be removed. The n-type impurities maybe any of the n-type impurities previously discussed, and the p-typeimpurities may be any of the p-type impurities previously discussed. Thelightly doped source/drain regions may have a concentration ofimpurities of from about 10¹⁵ cm⁻³ to about 10¹⁶ cm⁻³. An anneal may beused to activate the implanted impurities.

Epitaxial source/drain regions 70 are then formed in the fins 52. Theepitaxial source/drain regions 70 are formed in the fins 52 such thatthe dummy gates 62 are disposed between respective neighboring pairs ofthe epitaxial source/drain regions 70. In some embodiments the epitaxialsource/drain regions 70 may extend into portions of the fins 52 beneaththe top surfaces of the STI regions 56. In some embodiments, the gatespacers 66 are used to separate the epitaxial source/drain regions 70from the dummy gates 62 by an appropriate lateral distance so that theepitaxial source/drain regions 70 do not short out subsequently formedgates of the resulting FinFETs. The epitaxial source/drain regions 70can exert stress in respective channel regions 58 of the fins 52,thereby improving performance.

As a result of the epitaxy processes used to form the epitaxialsource/drain regions 70, upper surfaces of the epitaxial source/drainregions 70 have facets which expand laterally outward beyond sidewallsof the fins 52. In some embodiments, these facets cause adjacentepitaxial source/drain regions 70 of a same FinFET to merge asillustrated by FIG. 2C. For example, merged epitaxial source/drainregions 70 may be formed when one transistor is formed from multiplefins, e.g., a fin group 52G. In other embodiments, adjacent source/drainregions 70 remain separated after the epitaxy process is completed asillustrated by FIG. 2D. For example, unmerged epitaxial source/drainregions 70 may be formed when one transistor is formed from a single fin52S. In the embodiments illustrated in FIGS. 2C and 2D, gate spacers 66are formed covering a portion of the sidewalls of the fins 52 thatextend above the STI regions 56, thereby blocking the epitaxial growth.In some other embodiments, the spacer etch used to form the gate spacers66 may be adjusted to remove the spacer material to allow theepitaxially grown region to extend to the surface of the STI region 56.

In FIGS. 3A and 3B, a first ILD layer 74 is deposited over theintermediate structure. The first ILD layer 74 may be formed of adielectric material, and may be deposited by any suitable method, suchas CVD, plasma-enhanced CVD (PECVD), or FCVD. Dielectric materials mayinclude Phospho-Silicate Glass (PSG), Boro-Silicate Glass (BSG),Boron-Doped Phospho-Silicate Glass (BPSG), undoped Silicate Glass (USG),or the like. Other insulation materials formed by any acceptable processmay be used. In some embodiments, a contact etch stop layer (CESL) 72 isdisposed between the first ILD layer 74 and the epitaxial source/drainregions 70, the masks 64, and the gate spacers 66. The CESL 72 maycomprise a dielectric material, such as, silicon nitride, silicon oxide,silicon oxynitride, or the like, having a different etch rate than thematerial of the first ILD layer 74.

In FIGS. 4A and 4B, a planarization process, such as a CMP, may beperformed to level the top surface of the first ILD layer 74 with thetop surfaces of the dummy gates 62 or the masks 64. The planarizationprocess may also remove the masks 64 on the dummy gates 62, and portionsof the gate spacers 66 along sidewalls of the masks 64. After theplanarization process, top surfaces of the dummy gates 62, the gatespacers 66, and the first ILD layer 74 are level. Accordingly, the topsurfaces of the dummy gates 62 are exposed through the first ILD layer74. In some embodiments, the masks 64 may remain, in which case theplanarization process levels the top surface of the first ILD layer 74with the top surfaces of the top surface of the masks 64.

In FIGS. 5A and 5B, the dummy gates 62 are removed and are replaced withmetal gates 80. The metal gates 80 include gate dielectrics 82 and gateelectrodes 84. As an example to form the metal gates 80, the dummy gates62, and the masks 64 if present, are removed in one or more etchingstep(s), so that recesses are formed. Portions of the dummy gatedielectrics 60 in the recesses may also be removed. In some embodiments,only the dummy gates 62 are removed and the dummy gate dielectrics 60remain and are exposed by the recesses. In some embodiments, the dummygate dielectrics 60 are removed from recesses in a first region of a die(e.g., a core logic region) and remain in recesses in a second region ofthe die (e.g., an input/output region). In some embodiments, the dummygates 62 are removed by an anisotropic dry etch process. For example,the etching process may include a dry etch process using reactiongas(es) that selectively etch the dummy gates 62 without etching thefirst ILD layer 74 or the gate spacers 66. The recesses expose the fins52. Specifically, the channel regions 58 are exposed by the recesses.Each channel region 58 is disposed between neighboring pairs of theepitaxial source/drain regions 70. During the removal, the dummy gatedielectrics 60 may be used as etch stop layers when the dummy gates 62are etched. The dummy gate dielectrics 60 may then be optionally removedafter the removal of the dummy gates 62. After the removal, the gatedielectrics 82 are deposited conformally in the recesses, such as on thetop surfaces and the sidewalls of the fins 52 and on sidewalls of thegate spacers 66. The gate dielectrics 82 may also be formed on topsurface of the first ILD layer 74. In accordance with some embodiments,the gate dielectrics 82 comprise silicon oxide, silicon nitride, ormultilayers thereof. In some embodiments, the gate dielectrics 82include a high-k dielectric material, and in these embodiments, the gatedielectrics 82 may have a k value greater than about 7.0, and mayinclude a metal oxide or a silicate of Hf, Al, Zr, La, Mg, Ba, Ti, Pb,and combinations thereof. The formation methods of the gate dielectrics82 may include Molecular-Beam Deposition (MBD), atomic layer deposition(ALD), PECVD, and the like. In embodiments where portions of the dummygate dielectrics 60 remain in the recesses, the gate dielectrics 82include a material of the dummy gate dielectrics 60 (e.g., SiO₂). Thegate electrodes 84 are deposited over the gate dielectrics 82,respectively, and fill the remaining portions of the recesses. The gateelectrodes 84 may include a metal-containing material such as TiN, TiO,TaN, TaC, Co, Ru, Al, W, combinations thereof, or multi-layers thereof.For example, although a single-layered gate electrode 84 is illustrated,each gate electrode 84 may comprise any number of liner layers, anynumber of work function tuning layers, and a fill material. After thefilling of the gate electrodes 84, a planarization process, such as aCMP, may be performed to remove the excess portions of the gatedielectrics 82 and the material of the gate electrodes 84, which excessportions are over the top surface of the first ILD layer 74. Theremaining portions of material of the gate electrodes 84 and the gatedielectrics 82 thus form replacement gates of the resulting FinFETs. Themetal gates 80 may be also referred to as “gate stacks” or “replacementgate stacks.” The metal gates 80 may extend along sidewalls of a channelregion 58 of the fins 52.

The formation of the gate dielectrics 82 in the region 50N and theregion 50P may occur simultaneously such that the gate dielectrics 82 ineach region are formed from the same materials, and the formation of thegate electrodes 84 may occur simultaneously such that the gateelectrodes 84 in each region are formed from the same materials. In someembodiments, the gate dielectrics 82 in each region may be formed bydistinct processes, such that the gate dielectrics 82 may be differentmaterials, and/or the gate electrodes 84 in each region may be formed bydistinct processes, such that the gate electrodes 84 may be differentmaterials. Various masking steps may be used to mask and exposeappropriate regions when using distinct processes.

FIGS. 6A through 10B are various views of further intermediate stages inthe manufacturing of FinFETs, in accordance with some embodiments. FIGS.6A, 7A, 8A, 9A, and 10A are cross-sectional views illustrated alongreference cross-section A-A in FIG. 1. FIGS. 6B, 7B, 8B, 9B, and 10B aretop-down views.

FIGS. 6A through 10B show an embodiment where epitaxial source/drainregions 70 are not formed adjacent to all of the metal gates 80. Some ofthe metal gates 80 can be adjacent to one or no epitaxial source/drainregions 70. For example, FIG. 6A illustrates metal gates 80A that areadjacent to pairs of epitaxial source/drain regions 70 and overrespective channel regions 58, and also illustrates metal gates 80B thatare adjacent to only one epitaxial source/drain region 70 and are notformed over respective channel regions.

Further, FIGS. 6A through 10B show an embodiment where a transistor isformed from multiple fins, e.g., a fin group 52G (see FIG. 2C). Thus,contacts to the epitaxial source/drain regions 70 (discussed furtherbelow) will extend over respective fin groups 52G. It should beappreciated that similar techniques as those discussed below may be usedfor embodiments where a transistor is formed from a single fin 52S (seeFIG. 2D).

In FIG. 6A, one or more masking layer(s) 90 are formed over the metalgates 80 and first ILD layer 74. FIG. 6B is a top-down view, where FIG.6A is illustrated along reference cross-section A-A in FIG. 6B, butwhere some features are omitted for clarity of illustration. In theembodiment shown, the masking layer(s) 90 are a multilayer structurecomprising a lower masking layer 90A and an upper masking layer 90B onthe lower masking layer 90A. In some embodiments, a single masking layer90 is used. A cut mask 92 is then formed over the masking layer(s) 90.The cut mask 92 has cut openings 94 exposing the masking layer(s) 90,such as the upper masking layer 90B in embodiments where the maskinglayer(s) 90 comprise a multilayer.

The lower masking layer 90A is formed over the over the metal gates 80and first ILD. The lower masking layer 90A may be formed of a materialthat includes a metal (e.g., titanium nitride, titanium, tantalumnitride, tantalum, a metal-doped carbide (e.g., tungsten carbide), orthe like) and/or a metalloid (e.g., silicon nitride, boron nitride,silicon carbide, or the like). In some embodiments, a materialcomposition of the lower masking layer 90A is determined to provide ahigh etch selectivity with respect to other layers, such as the firstILD layer 74, and/or to subsequently formed layers, such as the uppermasking layer 90B (described in greater detail below). The lower maskinglayer 90A may be formed by a process such as chemical vapor deposition(CVD), ALD, or the like. Other processes and materials may be used. Insome embodiments, the lower masking layer 90A has a thickness in therange of about 15 nm to about 20 nm, although in other embodiments thelower masking layer 90A may have another thickness. In subsequentprocessing steps, a pattern is formed in the lower masking layer 90Ausing patterning techniques described herein. The lower masking layer90A is then used as an etching mask for etching the first ILD layer 74,in which the pattern of the lower masking layer 90A is transferred tothe first ILD layer 74.

The upper masking layer 90B is formed on the lower masking layer 90A. Insubsequent processing steps, a pattern is formed in the upper maskinglayer 90B using patterning techniques described herein. The patternedupper masking layer 90B is then used as an etching mask for patterningthe lower masking layer 90A. The upper masking layer 90B may be formedfrom a silicon oxide, such as borophosphosilicatetetraethylorthosilicate (BPTEOS) or undoped tetraethylorthosilic ate(TEOS) oxide, and may be formed by CVD, ALD, plasma-enhanced atomiclayer deposition (PEALD), spin-on coating, or the like. The uppermasking layer 90B may include a Low-Temperature (LT) oxide layer, whichis deposited at a low temperature, for example, lower than about 100° C.In some embodiments, a material composition of the upper masking layer90B may be determined to provide a high etch selectivity with respect toother layers such as the lower masking layer 90A. The upper maskinglayer 90B may include more than one layer and may be formed of more thanone material. In some embodiments, the upper masking layer 90B has athickness in the range of about 38 nm to about 40 nm, although in otherembodiments the upper masking layer 90B may have another thickness. Insubsequent processing steps, a pattern is formed in the upper maskinglayer 90B using patterning techniques described herein.

The cut mask 92 is formed of a dielectric material that has a high etchselectivity with respect to the masking layer(s) 90, relative theetching process that will be used to pattern the cut openings 94. Forexample, the cut mask 92 can comprise an inorganic material, such as anitride (such as silicon nitride), an oxynitride (such as siliconoxynitride), an oxide (such as silicon oxide), or the like, and can beformed by a process such as CVD, ALD, spin-on coating, or the like. Insome embodiments, the cut mask 92 is formed of silicon nitride. As anexample of forming the cut mask 92, a layer of dielectric material canbe deposited to a thickness in the range of about 30 nm to about 35 nm.The layer of dielectric material can then be patterned with cut openings94 exposing the masking layer(s) 90. The cut openings 94 can bepatterned by acceptable photolithography and etching processes. Forexample an anisotropic wet etch can be performed using a photoresist asan etching mask to pattern the cut openings 94.

The cut mask 92 has cut portions 92C and trim portions 92T. The cutportions 92C are strips, and may have substantially uniform widths inthe top view. Furthermore, the cut portions 92C run perpendicular to andoverlap the metal gates 80, but run parallel to and do not overlap thefins 52. Each cut portion 92C is laterally disposed between one or morefins 52, such as directly over features that are disposed between theone or more fins 52. Each cut portion 92C is laterally disposed betweenrespective fin groups 52G (or respective fins 52S, see FIG. 2D). Inother words, a fin group 52G (or fin 52S, see FIG. 2D) is laterallydisposed between a neighboring pair of the cut portions 92C. Asdiscussed further below, the cut portions 92C define where cuts arelocated between subsequently formed contacts. The trim portions 92T areperpendicular to the cut portions 92C, e.g., the trim portions 92T runperpendicular to and overlap the fins 52, but run parallel to and do notoverlap the metal gates 80. Each trim portion 92T is laterally disposedbetween two metal gates 80, such as directly over features that aredisposed between two metal gates 80. Each trim portion 92T extends overfin group 52G (or a respective fin 52S, see FIG. 2D), and connects thecut portions 92C that extend along the respective fin group 52G (or therespective fin 52S, see FIG. 2D). As discussed further below, the trimportions 92T define where contacts will not be subsequently formed.

As shown in FIG. 6A, some unused regions 52U of the fins 52 (also calleddummy regions) do not contain epitaxial source/drain regions 70, andsome regions of the fins 52 do not contain channel regions 58. Theunused regions 52U of the fins 52 can be disposed between the metalgates 80B, e.g., between metal gates 80 that are not disposed betweenrespective neighboring pairs of the epitaxial source/drain regions 70.The CESL 72 directly contacts and extends along the top surfaces of theunused regions 52U of the fins 52. Specifically, pairs of the gatespacers 66 can expose unused regions 52U of the fins 52, with the CESL72 extending continually over portions of the fins 52 between the pairof gate spacers 66 and along sidewalls of the gate spacers 66. Inaccordance with some embodiments, the trim portions 92T are formed overthe unused regions 52U of each of the fins 52. As noted above, the trimportions 92T define where contacts will not be subsequently formed.Because there are no epitaxial source/drain regions 70 in the unusedregions 52U of the fins 52, any contacts formed to the unused regions52U of the fins 52 would be electrically isolated and remain unused,e.g., would be dummy contacts. Such dummy contacts would induce aparasitic capacitance on adjacent metal gates 80. By forming the trimportions 92T over the unused regions 52U of the fins 52, the formationof undesirable dummy contacts to the unused regions 52U of the fins 52may be avoided. Specifically, all dielectric features (e.g., the gatespacers 66, CESL 72, and first ILD layer 74) that are over the unusedregions 52U of the fins 52 and between the metal gates 80B are free ofconductive features.

As shown in FIG. 6B, the cut openings 94 are defined by the cut portions92C and trim portions 92T. Some cut openings 94 are defined by two cutportions 92C and two trim portions 92T. Specifically, at least some ofthe cut openings 94R can have regular shapes in the top-down view, e.g.,quadrilateral shapes, where the cut openings 94R are defined by fourstraight segments of the dielectric material of the cut mask 92.Conversely, other cut openings 94N have irregular shapes in the top-downview, and are defined by more than four straight segments of thedielectric material of the cut mask 92. For example, the cut openings94N can be defined by more than two cut portions 92C and more than twotrim portions 92T.

The cut openings 94 can have various shapes and sizes, depending on thepositions and lengths of the cut portions 92C and trim portions 92T.However, the minimum dimensions of the cut openings 94R can beconstrained based on the limits of a photography process that will beused to pattern subsequently formed contacts, and based on the width W₁and pitch P₁ of the fins 52 (see FIG. 2B). Further, adjacent trimportions 92T can be formed close together. Continuing the example fromabove, the distance between cut portions 92C can be constrained to aminimum distance D₁, which can be in the range of about 30 nm to about42 nm, and the minimum distance between trim portions 92T can also beconstrained to a minimum distance D₂, which can be in the range of about50 nm to about 100 nm. In this embodiment, the distance D₂ can be lessthan the distance D₁. Further, the trim portions 92T are formed to awidth W₂, which is measured along a direction parallel to thelongitudinal axes of the fins 52. The width W₂ can be in the range ofabout 30 nm to about 40 nm. Constraining the dimensions of the openings94R allows the first ILD layer 74 to be patterned without under-etching,particularly when multiple masks (e.g., the cut mask 92 and the linemask 96) are used to pattern the first ILD layer 74.

In FIG. 7A, a line mask 96 is formed on the cut mask 92 and on theportions of the masking layer(s) 90 exposed by the cut openings 94. FIG.7B is a top-down view, where FIG. 7A is illustrated along referencecross-section A-A in FIG. 7B, but where some features are omitted forclarity of illustration. The line mask 96 has slot openings 98 exposingthe underlying cut mask 92 and masking layer(s) 90. The slot openings 98in the line mask 96 define regions in which contacts will be formed inthe first ILD layer 74 and coupled to the epitaxial source/drain regions70 of the resulting FinFETs. As discussed further below, the cutopenings 94 in the cut mask 92 define where cuts are located between thecontacts subsequently formed in the first ILD layer 74. Some portions ofthe line mask 96 are formed in the openings 94R (see FIG. 6B).

The line mask 96 can be formed of a photoresist, such as a single layerphotoresist, a bi-layer photoresist, a tri-layer photoresist, or thelike. In some embodiments, the line mask 96 is a tri-layer maskcomprising a bottom layer (e.g., a bottom anti-reflective coating (BARC)layer), a middle layer (e.g., a nitride, an oxide, an oxynitride, or thelike), and a top layer (e.g., a photoresist). The type of mask used(e.g., single layer mask, bilayer mask, tri-layer mask, etc.) may dependon the photolithography process used to pattern the line mask 96. Forexample, in extreme ultraviolet (EUV) lithography processes, the linemask 96 may be a single layer mask or a bilayer mask. The line mask 96can be patterned using acceptable photolithography techniques to formthe slot openings 98. The slot openings 98 are strips, and may havesubstantially uniform widths in the top view. Furthermore, the slotopenings 98 run perpendicular to and overlap the fins 52, but runparallel to and do not overlap the metal gates 80. The slot openings 98also overlap the first ILD layer 74 and cut mask 92. The overlap regionsbetween the slot openings 98 and cut mask 92 correspond to the cuts thatwill be located between the contacts subsequently formed in the firstILD layer 74.

The slot openings 98 are formed to a width W₃, which is measured along adirection parallel to the longitudinal axes of the fins 52. The width W₃can be in the range of about 13 nm to about 15 nm. Notably, the width W₃of the slot openings 98 is less than the width W₂ of the trim portions92T of the cut mask 92 (see FIG. 6B). By constraining the width W₃ to beless than the width W₂, the unused regions 52U of the fins 52 can remainfully protected during subsequent patterning so that the formation ofundesirable dummy contacts to the unused regions 52U of the fins 52 maybe avoided.

In FIG. 8A, the masking layer(s) 90 are etched using the line mask 96and cut mask 92 (see FIG. 7A) as a combined etching mask to extend theslot openings 98 through the masking layer(s) 90. FIG. 8B is a top-downview, where FIG. 8A is illustrated along reference cross-section A-A inFIG. 8B, but where some features are omitted for clarity ofillustration. During the etching, the cut mask 92 acts as an etch stoplayer to prevent the slot openings 98 from extending into the portionsof the masking layer(s) 90 directly underlying the cut mask 92. In otherwords, the portions of the first ILD layer 74 uncovered by the line mask96 and cut mask 92 (and thus exposed by the slot openings 98 and cutopenings 94) are etched. The etching may be anisotropic, so that theslot openings 98 are extended through the masking layer(s) 90 and haveabout the same sizes in the masking layer(s) 90 as they do in the linemask 96. The etching can comprise one or more etch process(es) thatattack the masking layer(s) 90, but do not attack the cut mask 92. Forexample, when the masking layer(s) 90 comprise a multilayer, a firstetching process may be performed to pattern the upper masking layer 90B,and a second etching process may be performed to pattern the lowermasking layer 90A.

The first etching process may include a dry etching process having ahigh etching selectivity of the upper masking layer 90B relative to thelower masking layer 90A and cut mask 92. In some embodiments, the dryetching process may include an inductively-coupled plasma generated witha power in the range of about 150 Watts to about 1500 Watts and may beperformed at a pressure in the range of about 3 mTorr to about 80 mTorr.In some embodiments, the dry etching process may use a fluorine-basedetchant gas such as CF₄, CH₂F₂, CHF₃, or another type of process gas.Other etching techniques may be used in other embodiments. During theetching of the upper masking layer 90B, the line mask 96 may be at leastpartially consumed. In embodiments when the line mask 96 is notcompletely consumed while etching the upper masking layer 90B, asuitable removal process (e.g., an ashing or stripping process) may beperformed to remove remaining residue of the line mask 96.

The second etching process may include a wet etching process having ahigh etching selectivity of the lower masking layer 90A relative to theupper masking layer 90B, first ILD layer 74, and cut mask 92. In someembodiments, the wet etching process may use an etchant such as dilutehydrofluoric acid (dilute HF), de-ionized water (DIW), SC-1 (e.g., acombination of DIW, ammonia water, and aqueous H₂O₂) or the like, andmay be performed at a temperature in the range of about 50° C. to about70° C. Other etching techniques may be used in other embodiments. Afterthe second etching process, portions of the first ILD layer 74 areexposed. Any remaining portions of the cut mask 92 can then be removed,such as by a wet clean process.

Using two masks (e.g., the line mask 96 and cut mask 92) pattern theslot openings 98 in the masking layer(s) 90 allows uniformity of thepattern in the masking layer(s) 90 to be maintained. Specifically,forming the line mask 96 with slot openings 98 allows a uniform distancebetween the slot openings 98 to be maintained, and forming the cut mask92 with cut portions 92C allows a uniform distance between cuts to bemaintained.

The first ILD layer 74 is then etched using the patterned maskinglayer(s) 90 as an etching mask to extend the slot openings 98 throughthe first ILD layer 74 and CESL 72. The slot openings 98 may be extendedusing acceptable etching techniques. For example, the slot openings 98can be extended through the first ILD layer 74 using a first etchingprocess, and the CESL 72 can then be opened using a second etchingprocess. The masking layer(s) 90 may be consumed during the etching, ormay be removed after the etching. Removal may be by, e.g., a wet cleanprocess, a CMP process, or the like.

The slot openings 98 expose the epitaxial source/drain regions 70 andportions of the STI regions 56. As noted above, the trim portions 92T ofthe cut mask 92 (see FIG. 6B) define where slot openings 98 will not beformed, with the trim portions 92T being formed over the unused regions52U of the fins 52. As a result, each of the slot openings 98 exposes atleast one epitaxial source/drain region 70. In other words, as shown inFIG. 8B, none of the slot openings 98 expose the unused regions 52U ofthe fins 52. Further, a subset of the slot openings 98S expose multipleepitaxial source/drain regions 70, and define regions in which sharedcontacts will be formed for the exposed epitaxial source/drain regions70. Advantageously, by avoiding the formation of slot openings 98 to theunused regions 52U of the fins 52, the formation of undesirable dummycontacts may be avoided.

In FIG. 9A, lower source/drain contacts 100 are formed in the slotopenings 98 (see FIGS. 8A and 8B). FIG. 9B is a top-down view, whereFIG. 9A is illustrated along reference cross-section A-A in FIG. 9B, butwhere some features are omitted for clarity of illustration. A liner,such as a diffusion barrier layer, an adhesion layer, or the like, and aconductive material are formed in the slot openings 98. The liner mayinclude titanium, titanium nitride, tantalum, tantalum nitride, or thelike. The conductive material may be copper, a copper alloy, silver,gold, tungsten, cobalt, aluminum, nickel, or the like. A planarizationprocess, such as a CMP, may be performed to remove excess material froma surface of the first ILD layer 74. The remaining liner and conductivematerial form the lower source/drain contacts 100 in the slot openings98. An anneal process may be performed to form a silicide at theinterface between the epitaxial source/drain regions 70 and the lowersource/drain contacts 100. The lower source/drain contacts 100 arephysically and electrically coupled to the epitaxial source/drainregions 70.

As noted above, the trim portions 92T of the cut mask 92 (see FIG. 6B)define where contacts will not be formed, with the trim portions 92Tbeing formed over the unused regions 52U of the fins 52. As a result,each of the lower source/drain contacts 100 is coupled to at least oneepitaxial source/drain region 70. In other words, none of the lowersource/drain contacts 100 are coupled to the unused regions 52U of thefins 52. Rather, all of the unused regions 52U of the fins 52 arecontacted by the CESL 72 (see FIG. 9A). Further, a subset of the lowersource/drain contacts 100S are formed in the slot openings 98S, and arethus coupled to multiple epitaxial source/drain regions 70. The lowersource/drain contacts 100S are shared contacts, which can be formed insome types of devices, such as memories, e.g., static random accessmemory (SRAM) cells.

As noted above, the slot openings 98 of the line mask 96 (see FIGS. 7Aand 7B) define where the lower source/drain contacts 100 will be formed.As also noted above, the slot openings 98 are strips. As a result, thelower source/drain contacts 100 are also strips, and extend acrossrespective fin groups 52G (or respective fins 52S, see FIG. 2D).Specifically, the lower source/drain contacts 100 have lengths L₁ alongtheir longitudinal axes and have widths W₄ along their latitudinal axes.The lengths L₁ are greater than the widths W₄, and the longitudinal axesof the lower source/drain contacts 100 are perpendicular to thelongitudinal axes of the fins 52 (see FIG. 9B). The longitudinal axes ofthe fins 52 and lower source/drain contacts 100 are parallel to a majorsurface of the substrate 50. Forming the lower source/drain contacts 100with a slotted mask allows the lower source/drain contacts 100 to beformed to small dimensions. For example, the lengths L₁ can be in therange of about 30 nm to about 40 nm, and the widths W₄ can be in therange of about 15 nm to about 18 nm.

In FIG. 10A, a second ILD layer 110 is deposited over the first ILDlayer 74 and lower source/drain contacts 100. FIG. 10B is a top-downview, where FIG. 10A is illustrated along reference cross-section A-A inFIG. 10B, but where some features are omitted for clarity ofillustration. In some embodiments, the second ILD layer 110 is aflowable film formed by a flowable CVD method. In some embodiments, thesecond ILD layer 110 is formed of a dielectric material such as PSG,BSG, BPSG, USG, or the like, and may be deposited by any suitablemethod, such as CVD and PECVD. In accordance with some embodiments,before the formation of the second ILD layer 110, the metal gates 80 canbe recessed, so that a recess is formed directly over the metal gates 80and between opposing portions of the gate spacers 66. A gate mask (notshown) comprising one or more layers of dielectric material, such assilicon nitride, silicon oxynitride, or the like, is filled in therecess, followed by a planarization process to remove excess portions ofthe dielectric material extending over the first ILD layer 74.

Gate contacts 114 and upper source/drain contacts 116 are then formedthrough the second ILD layer 110. Openings for the gate contacts 114 andupper source/drain contacts 116 are formed through the second ILD layer110. The openings may be formed using acceptable photolithography andetching techniques. A liner, such as a diffusion barrier layer, anadhesion layer, or the like, and a conductive material are formed in theopenings. The liner may include titanium, titanium nitride, tantalum,tantalum nitride, or the like. The conductive material may be copper, acopper alloy, silver, gold, tungsten, cobalt, aluminum, nickel, or thelike. A planarization process, such as a CMP, may be performed to removeexcess material from a surface of the second ILD layer 110. Theremaining liner and conductive material form the upper source/draincontacts 116 and gate contacts 114 in the openings. The uppersource/drain contacts 116 are physically and electrically coupled to thelower source/drain contacts 100, and the gate contacts 114 arephysically and electrically coupled to the metal gates 80. The gatecontacts 114 can penetrate through the gate mask, if present. The uppersource/drain contacts 116 and gate contacts 114 may be formed indifferent processes, or may be formed in the same process. Each of theupper source/drain contacts 116 and gate contacts 114 may be formed indifferent cross-sections, which may avoid shorting of the contacts.

Embodiments may achieve advantages. Forming the cut mask 92 with trimportions 92T allows unused regions 52U of the fins 52 to be protectedduring formation of the lower source/drain contacts 100. Specifically,the trim portions 92T of the cut mask 92 act as an etch stop layerduring the process for patterning the first ILD layer 74. Without thetrim portions 92T, dummy contacts would be formed to the unused regions52U of the fins 52. Although such dummy contacts would be electricallyisolated and unused in a final device, such dummy contacts would inducea parasitic capacitance on adjacent metal gates 80. By avoiding theformation of dummy contacts entirely, such a parasitic capacitance maybe avoided or at least reduced. The performance of the resulting FinFETsmay thus be improved, particularly in some applications, such as ringoscillators, where performance can be improved by up to 1%.

FIGS. 11A through 12B are various views of further intermediate stagesin the manufacturing of FinFETs, in accordance with some embodiments.FIGS. 11A and 11B show a structure at a similar processing step as thatshown in FIGS. 6A and 6B. In this embodiment, a fin group 52G (or a fin52S, see FIG. 2D) is crossed by a single trim portion 92T instead of twotrim portions 92T. Thus, the cut openings 94 defined on either side ofthe trim portion 92T are irregular cut openings 94N. FIGS. 12A and 12Bshow a structure at a similar processing step as that shown in FIGS. 10Aand 10B. The unused regions 52U of the fins 52 can be bordered on allsides by lower source/drain contacts 100.

FIGS. 13A through 15B are various views of further intermediate stagesin the manufacturing of FinFETs, in accordance with some embodiments.FIGS. 13A and 13B show a structure at a similar processing step as thatshown in FIGS. 6A and 6B. In this embodiment, a fin group 52G (or a fin52S, see FIG. 2D) is crossed by a two trim portion 92T, and the distanceD₂ between the trim portions 92T is larger, so that the openings 94R canbe large enough to accommodate the formation of a lower source/draincontact 100 for an underlying epitaxial source/drain region 70. In thisembodiment, the distance D₂ can be greater than the distance D₁.Specifically, the trim portions 92T can be close enough that theopenings 94R are large enough to accommodate the formation of a singlelower source/drain contact 100 for a single epitaxial source/drainregion 70. FIGS. 14A and 14B show a structure at a similar processingstep as that shown in FIGS. 7A and 7B. In this embodiment, the centersof the openings 94R can be aligned with the centers of a correspondingslot opening 98R. FIGS. 15A and 15B show a structure at a similarprocessing step as that shown in FIGS. 10A and 10B. As shown, one lowersource/drain contact 100R is formed in the area defined by the opening94R. Specifically, the lower source/drain contact 100R and itscorresponding epitaxial source/drain region 70 are laterally disposedbetween neighboring pairs of the unused regions 52U of the fins 52.

In an embodiment, a method includes: forming a first fin extending froma semiconductor substrate; growing a source/drain region in the firstfin; forming a metal gate over the first fin, the metal gate disposedbetween the source/drain region and a first dummy region of the firstfin; depositing an inter-layer dielectric (ILD) layer over thesource/drain region and the first dummy region; forming a cut mask overthe ILD layer, the cut mask having a first cut portion, a second cutportion, and a first trim portion, the first cut portion and the secondcut portion each extending along a longitudinal axis of the first fin,the first fin laterally disposed between the first cut portion and thesecond cut portion, the first trim portion connecting the first cutportion to the second cut portion, the first trim portion disposed overthe first dummy region; patterning a contact opening in the ILD layerusing the cut mask as an etching mask, portions of the ILD layer beneaththe first trim portion remaining over the first dummy region after thepatterning; and forming a source/drain contact in the contact opening,the source/drain contact coupled to the source/drain region.

In some embodiments, the method further includes: forming a second finextending from the semiconductor substrate, where the second fin islaterally disposed between the first cut portion and the second cutportion of the cut mask; growing the source/drain region in the secondfin; and forming the metal gate over the second fin, the metal gatedisposed between the source/drain region and a second dummy region ofthe second fin, where the first trim portion of the cut mask is disposedover the second dummy region. In some embodiments, the method furtherincludes: forming a contact etch stop layer (CESL) over the source/drainregion and the first dummy region, where the ILD layer is deposited overthe CESL; and etching the contact opening through the CESL, where theCESL physically contacts and extends across the first dummy region afteretching the contact opening. In some embodiments of the method,patterning the contact opening in the ILD layer using the cut mask asthe etching mask includes: forming a line mask over the cut mask, theline mask including a first slot opening, the first slot openingdisposed over the source/drain region, the first slot opening exposingthe first cut portion and the second cut portion of the cut mask; andetching the contact opening in portions of the ILD layer exposed by thefirst slot opening and uncovered by the first cut portion and the secondcut portion of the cut mask. In some embodiments of the method, the linemask includes a second slot opening, the second slot opening disposedover the first dummy region, the second slot opening exposing the firsttrim portion of the cut mask, and further including: etching portions ofthe ILD layer exposed by the second slot opening and uncovered by thefirst trim portion of the cut mask. In some embodiments of the method,the first trim portion of the cut mask has a first width, the secondslot opening has a second width, and the first width is greater than thesecond width. In some embodiments of the method, the cut mask has asecond trim portion, the second trim portion connecting the first cutportion to the second cut portion, the second trim portion disposed overa second dummy region of the first fin, where portions of the ILD layerbeneath the second trim portion remain over the second dummy regionafter the patterning. In some embodiments of the method, the first cutportion is separated from the second cut portion by a first distance,the first trim portion is separated from the second trim portion by asecond distance, and the second distance is greater than the firstdistance. In some embodiments of the method, the first distance is in arange of 30 nm to 42 nm, and the second distance is in a range of 50 nmto 100 nm.

In an embodiment, a method includes: forming fins extending from asemiconductor substrate; depositing an inter-layer dielectric (ILD)layer on the fins; forming masking layers on the ILD layer; forming acut mask on the masking layers, the cut mask including a firstdielectric material, the cut mask having first openings exposing themasking layers, each of the first openings surrounded on all sides bythe first dielectric material; forming a line mask on the cut mask andin the first openings, the line mask having slot openings, the slotopenings exposing portions of the cut mask and portions of the maskinglayers, the slot openings being strips extending perpendicular to thefins; patterning the masking layers by etching the portions of themasking layers exposed by the first openings and the slot openings; andetching contact openings in the ILD layer using the patterned maskinglayers as an etching mask.

In some embodiments of the method, the first dielectric material issilicon nitride, and the masking layers include a titanium nitride layerand a silicon oxide layer, the titanium nitride layer disposed betweenthe ILD layer and the silicon oxide layer. In some embodiments of themethod, patterning the masking layers includes: etching the siliconoxide layer with a dry etching process, where the dry etching processetches the silicon oxide layer at a greater rate than the cut mask; andetching the titanium nitride layer with a wet etching process, where thewet etching process etches the titanium nitride layer at a greater ratethan the cut mask. In some embodiments of the method, the dry etchingprocess is performed with an etchant including CF₄, CH₂F₂, or CHF₃. Insome embodiments of the method, the wet etching process is performedwith an etchant including dilute hydrofluoric acid, de-ionized water, ora combination of de-ionized water, ammonia water, and aqueous H₂O₂. Insome embodiments of the method, one of the first openings has a firstcenter, one of the slot openings has a second center, and the firstcenter is aligned with the second center. In some embodiments of themethod, a first subset of the first openings are surrounded on foursides by straight segments of the first dielectric material. In someembodiments of the method, a second subset of the first openings aresurrounded on more than four sides by straight segments of the firstdielectric material.

In an embodiment, a structure includes: a semiconductor substrate havinga major surface; a first fin extending from the semiconductor substrate,the first fin having a first longitudinal axis along a first direction,the first direction parallel to the major surface of the semiconductorsubstrate; a source/drain region in the first fin; a first metal gateover the first fin, the first metal gate disposed between thesource/drain region and a dummy region of the first fin; a second metalgate over the first fin, the dummy region disposed between the secondmetal gate and the first metal gate; a contact etch stop layer (CESL)over the source/drain region and the dummy region, the CESL physicallycontacting and extending continuously along the dummy region; a firstinter-layer dielectric (ILD) layer over the CESL; and a firstsource/drain contact extending through the first ILD layer and the CESL,the first source/drain contact physically contacting the source/drainregion, the first source/drain contact having a width and a length, thelength being greater than the width, the length being measured along asecond direction, the second direction being parallel to the majorsurface of the semiconductor substrate, the second direction beingperpendicular to the first direction.

In some embodiments, the structure further includes: a second ILD layerover the first ILD layer and the first source/drain contact; and ansecond source/drain contact extending through the second ILD layer, thesecond source/drain contact physically contacting the first source/draincontact. In some embodiments, the structure further includes: a firstgate spacer adjacent the first metal gate; and a second gate spaceradjacent the second metal gate, where no conductive features aredisposed in portions of the CESL and the first ILD layer disposed overthe first fin and between the first gate spacer and the second gatespacer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: forming a first finextending from a semiconductor substrate; growing a source/drain regionin the first fin; forming a metal gate over the first fin, the metalgate disposed between the source/drain region and a first dummy regionof the first fin; depositing an inter-layer dielectric (ILD) layer overthe source/drain region and the first dummy region; forming a cut maskover the ILD layer, the cut mask having a first cut portion, a secondcut portion, and a first trim portion, the first cut portion and thesecond cut portion each extending along a longitudinal axis of the firstfin, the first fin laterally disposed between the first cut portion andthe second cut portion, the first trim portion connecting the first cutportion to the second cut portion, the first trim portion disposed overthe first dummy region; patterning a contact opening in the ILD layerusing the cut mask as an etching mask, portions of the ILD layer beneaththe first trim portion remaining over the first dummy region after thepatterning; and forming a source/drain contact in the contact opening,the source/drain contact coupled to the source/drain region.
 2. Themethod of claim 1 further comprising: forming a second fin extendingfrom the semiconductor substrate, wherein the second fin is laterallydisposed between the first cut portion and the second cut portion of thecut mask; growing the source/drain region in the second fin; and formingthe metal gate over the second fin, the metal gate disposed between thesource/drain region and a second dummy region of the second fin, whereinthe first trim portion of the cut mask is disposed over the second dummyregion.
 3. The method of claim 1 further comprising: forming a contactetch stop layer (CESL) over the source/drain region and the first dummyregion, wherein the ILD layer is deposited over the CESL; and etchingthe contact opening through the CESL, wherein the CESL physicallycontacts and extends across the first dummy region after etching thecontact opening.
 4. The method of claim 1, wherein patterning thecontact opening in the ILD layer using the cut mask as the etching maskcomprises: forming a line mask over the cut mask, the line maskcomprising a first slot opening, the first slot opening disposed overthe source/drain region, the first slot opening exposing the first cutportion and the second cut portion of the cut mask; and etching thecontact opening in portions of the ILD layer exposed by the first slotopening and uncovered by the first cut portion and the second cutportion of the cut mask.
 5. The method of claim 4, wherein the line maskcomprises a second slot opening, the second slot opening disposed overthe first dummy region, the second slot opening exposing the first trimportion of the cut mask, and further comprising: etching portions of theILD layer exposed by the second slot opening and uncovered by the firsttrim portion of the cut mask.
 6. The method of claim 5, wherein thefirst trim portion of the cut mask has a first width, the second slotopening has a second width, and the first width is greater than thesecond width.
 7. The method of claim 1, wherein the cut mask has asecond trim portion, the second trim portion connecting the first cutportion to the second cut portion, the second trim portion disposed overa second dummy region of the first fin, wherein portions of the ILDlayer beneath the second trim portion remain over the second dummyregion after the patterning.
 8. The method of claim 7, wherein the firstcut portion is separated from the second cut portion by a firstdistance, wherein the first trim portion is separated from the secondtrim portion by a second distance, and wherein the second distance isgreater than the first distance.
 9. The method of claim 8, wherein thefirst distance is in a range of 30 nm to 42 nm, and the second distanceis in a range of 50 nm to 100 nm.
 10. A method comprising: forming finsextending from a semiconductor substrate; depositing an inter-layerdielectric (ILD) layer on the fins; forming masking layers on the ILDlayer; forming a cut mask on the masking layers, the cut mask comprisinga first dielectric material, the cut mask having first openings exposingthe masking layers, each of the first openings surrounded on all sidesby the first dielectric material; forming a line mask on the cut maskand in the first openings, the line mask having slot openings, the slotopenings exposing portions of the cut mask and portions of the maskinglayers, the slot openings being strips extending perpendicular to thefins; patterning the masking layers by etching the portions of themasking layers exposed by the first openings and the slot openings; andetching contact openings in the ILD layer using the patterned maskinglayers as an etching mask.
 11. The method of claim 10, wherein the firstdielectric material is silicon nitride, and wherein the masking layerscomprise a titanium nitride layer and a silicon oxide layer, thetitanium nitride layer disposed between the ILD layer and the siliconoxide layer.
 12. The method of claim 11, wherein patterning the maskinglayers comprises: etching the silicon oxide layer with a dry etchingprocess, wherein the dry etching process etches the silicon oxide layerat a greater rate than the cut mask; and etching the titanium nitridelayer with a wet etching process, wherein the wet etching process etchesthe titanium nitride layer at a greater rate than the cut mask.
 13. Themethod of claim 12, wherein the dry etching process is performed with anetchant comprising CF₄, CH₂F₂, or CHF₃.
 14. The method of claim 12,wherein the wet etching process is performed with an etchant comprisingdilute hydrofluoric acid, de-ionized water, or a combination ofde-ionized water, ammonia water, and aqueous H₂O₂.
 15. The method ofclaim 10, wherein one of the first openings has a first center, whereinone of the slot openings has a second center, and wherein the firstcenter is aligned with the second center.
 16. The method of claim 10,wherein a first subset of the first openings are surrounded on foursides by straight segments of the first dielectric material.
 17. Themethod of claim 16, wherein a second subset of the first openings aresurrounded on more than four sides by straight segments of the firstdielectric material.
 18. A structure comprising: a semiconductorsubstrate having a major surface; a first fin extending from thesemiconductor substrate, the first fin having a first longitudinal axisalong a first direction, the first direction parallel to the majorsurface of the semiconductor substrate; a source/drain region in thefirst fin; a first metal gate over the first fin, the first metal gatedisposed between the source/drain region and a dummy region of the firstfin; a second metal gate over the first fin, the dummy region disposedbetween the second metal gate and the first metal gate; a contact etchstop layer (CESL) over the source/drain region and the dummy region, theCESL physically contacting and extending continuously along the dummyregion; a first inter-layer dielectric (ILD) layer over the CESL; and afirst source/drain contact extending through the first ILD layer and theCESL, the first source/drain contact physically contacting thesource/drain region, the first source/drain contact having a width and alength, the length being greater than the width, the length beingmeasured along a second direction, the second direction being parallelto the major surface of the semiconductor substrate, the seconddirection being perpendicular to the first direction.
 19. The structureof claim 18 further comprising: a second ILD layer over the first ILDlayer and the first source/drain contact; and an second source/draincontact extending through the second ILD layer, the second source/draincontact physically contacting the first source/drain contact.
 20. Thestructure of claim 18 further comprising: a first gate spacer adjacentthe first metal gate; and a second gate spacer adjacent the second metalgate, wherein no conductive features are disposed in portions of theCESL and the first ILD layer disposed over the first fin and between thefirst gate spacer and the second gate spacer.